<style>
.button{
  display: inline-block;
  outline: none;
  cursor: pointer;
  text-align: center;
  text-decoration: none;
  font: 14px/100% Arial,Helvetica,sans-serif;
  padding: .5em 2em .55em;
  text-shadow: 0 1px 1px rgba(0,0,0,.3);
  border-radius: .5em;
  box-shadow: 0 1px 2px rgba(0,0,0,.2);
  color: white;
  border: solid 1px ;
}
</style>
<div class="button orange">123</div>
<script>
var btn=document.querySelector('.button');
var h=25;
setInterval(function(){
  h++;
  h=h%360;
  btn.style.borderColor=`hsl(${h},95%,45%)`
  btn.style.background=`linear-gradient(to bottom, hsl(${h},95%,54.1%),hsl(${h},95%,84.1%))`
},100)
</script>